Growing outbreaks of whooping cough — including a California epidemic that has killed six babies — are worrying public health officials who fear that sporadic vaccination practices may be contributing to dangerous cases of the preventable disease.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

"I'm saddened, but I can't truly say I'm surprised," said Dr. Saad B. Omer, an assistant professor with Emory University's Rollins School of Public Health and an national expert on immunization practices. "We know and we have known for a while that we have these gaps in protection at the local level."

Rising cases of the disease also known as pertussis have been reported in Idaho, Texas, South Carolina, Michigan and in California, where 1,500 children have been diagnosed in what's being called the worst outbreak in 50 years.

In some places, including Michigan and California, there are communities where parents have refused recommended vaccinations, often because they fear complications from the shots.

'Herd immunity' breached
When that happens, vaccine resisters breach what's known as "herd immunity," the necessary level of protection that keeps disease from spreading. That allows infection to infect vulnerable people, including those for whom a vaccine doesn't work or wears off, and babies too young to be immunized.

There's some evidence that being under-vaccinated or not vaccinated at all is contributing to a portion of the cases in the California outbreak and others, said Dr. Tom Clark, a medical epidemiologist with the federal Centers for Disease Control and Prevention. He declined to say what proportion of the ill children in California were not fully vaccinated.

In other cases, the illness is showing up in children ages 7 to 10, kids whose older vaccinations may be waning, but who have not yet received recommended doses for adolescents.

Vaccines for pertussis are given to children at 2, 4 and 6 months and then again at about age 11 or 12. Experts also recommend that adults who are around children under the age of 1 get vaccinated.

Pertussis is a bacterial infection that can cause uncontrollable coughing and respiratory distress. It's dubbed "whooping cough" because of the sound a victim makes trying to catch breath between bouts of coughing. Peak season is late summer and early fall, which may mean more outbreaks ahead.

Whooping cough outbreaks tend to run in three- to five- year cycles, said Chris Van Deusen of the Texas Department of State Health Services. There, outbreaks have been seen in pockets across the state with the biggest increase in Central Texas areas.

"There it's significantly higher than the usual rates but it's not a statewide problem," said Van Deusen said.

Counties report more cases
Some counties in Michigan are reporting more cases so far this year than in the past 10 years. South Carolina has 168 reported cases so far this year, higher than those reported during the same time period since 2006. In Idaho, 77 cases of whooping cough have been reported in in the first six months of the year, according to the Idaho Department of Health and Welfare. That's up from 45 cases reported in the same period last year.

Idaho state epidemiologist Dr. Christine Hahn says the department is encouraging families to get vaccinated against the illness. She says infants will be better protected against potentially fatal whooping cough if adults and adolescents in their families have up-to-date vaccinations or booster shots.

In 2009, a study showed that children who don't get whooping cough vaccine are 23 times more likely to get the disease than vaccinated kids. The study, published in Pediatrics, was of 751 children in Kaiser Permamente of Colorado's health plan.

But Barbara Loe Fisher, president and co-founder of the National Vaccine Information Center, which generally opposes vaccination, says that parents who choose not to immunize their kids can't be blamed for the growing outbreaks.

Pertussis can infect even vaccinated people, and the vaccines aren't always effective, she said. In addition, the pertussis bacteria may be becoming resistant to the vaccines, something the CDC is investigating, Clark said. She urged parents to consider their options carefully.

"It's always a balance to weigh the risk of the complications of pertussis, which can be serious for some children, and the risks, known and unknown, of the vaccines," Fisher said.

Video: Whooping cough breaks out in California

Closed captioning of: Whooping cough breaks out in California

>>>back now with the comeback of
whooping cough
. the worst outbreak in 50 years. nearly
1500
confirmed cases and at least six infants have die. dr.
nancy snyderman
joins us.

>>hey, meredith. i think we are seeing a tipping point in unvaccinated children. the
hot pockets
are in families where, frankly, parents have decided not to vaccinate their children. in morin county near
san francisco
there are more cases than anywhere else. six infants have lost their lives who, frankly, should not have died.

>>you say the vaccines have become victims of their own success. what do you mean?

>>you and i remember what it was like in the '50s and '60s when we were lined up for the
polio vaccine
. the idea was if you get a vaccination you will not get ill and will not die. we had mass inoculations. people forget what it was like to see people with these
communicable diseases
. i worry if we undervaccinate children and you see
whooping cough
coming back, this is the canary in the
coal mines
. last year we saw children dying of measles. these infectious and deadly diseases shouldn't even be talked about.

>>the
whooping cough
season is just beginning.

>>it is. august and september we may see more.

>>how do people protect themselves at this point?

>>i have been an unabashed advocate for vaccinations. they are safe. they work. a lot of people are opting out saying, it's against my religion. for most people that's not true. make sure your children are vaccinated. the
whooping cough
vaccine is given at 2, 4, 6 months. if you are an adult and around a child under the age of 1, get vaccinated. if you are a woman of child-bearing years, get vaccinated. pull out the card your pediatrician gives you. there is a
vaccination schedule
you can get. these vaccines are meant to protect your children and you. if you think you can opt out, remember that when you go to the grocery store and walk by someone with cancer, m.s. or any other compromised immune system you put that person in harm's way, too. there is a time when the community as a whole's needs are more important than the individual's. right now individuals are trumping the general populous and i find it offensive and a amoral.

>>what do you see for symptoms?

>>starts as a crummy cold but then you get this
whooping cough
. it may start as stuffy knownose, sniffles. one to two weeks later children are fighting to breathe. when they die they suffocate themselves because they struggle for breath. i have seen several cases as a young pediatrician. it is a horrendous disease. any time we talk about something that can be prevented we have to go back to basics. this is a time. make sure your children are safe.

>>is it likely this will spread to other states?

>>i have no doubt that it's going to. it peaked in california. last year in minnesota and in philadelphia we know children died of measles. this winter as
whooping cough
upticks, measles continues to be undervaccinated. we'll see pockets of communicable infections that a few decades ago we thought, frankly, we had eradicated from the
united states
. these illnesses should not be seen in the
united states
with the vaccinations we have at hand.